Discovering the mother of all Researchers trace bison to common ancestor, pinpoint arrival in .

By Katie Willis on March 13, 2017

Unlike other notorious invaders such as zebra mussels, bison were not introduced by humans. But their rapid spread and diversification are hallmarks of an invasive species.

Scientists from University of have pinpointed when bison “The DNA was too degraded, but as techniques have developed, first appeared in North America and learned more about their in particular new ways to 'fish out' bison DNA from the mixture of family tree, thanks to new fossils and genetic tools. bacterial and other DNA in these bones, these have allowed us to piece together these genome sequences,” explains Shapiro. New research by Duane Froese and Alberto Reyes in the Department of Earth and Atmospheric Sciences has identified The group showed that DNA of the earliest Yukon bison was North America’s oldest bison fossils and applied new techniques similar to DNA from a giant long-horned bison, called Bison for ancient DNA extraction to clarify the earliest parts of the bison latifrons, which was excavated in Colorado. family tree. “Bison latifrons is an interesting beast,” says Froese. “Its horns Froese and his colleagues worked with paleogeneticists to measured more than two metres across at the tips and it was sequence the mitochondrial genomes of more than 40 bison, perhaps 25% larger than modern bison.” including the two oldest bison fossils ever recovered: one from Ch’ijee’s Bluff in the Vuntut Gwitchin Territory in northern Yukon, The Colorado fossil was well-dated and only 10,000 to 20,000 and another from Snowmass, Colorado. Comparing these years younger than the Yukon fossils. And, despite being genomes to additional Siberian and North , the considered a different species based on skull morphology and researchers constructed an age-calibrated bison family tree and size, the genetics showed that the two fossils were closely related. established that a common maternal ancestor arrived between “In fact, this showed that all of the bison had a common ancestor 130,000 and 195,000 years ago. between about 130,000 and 195,000 years ago,” explains Froese. “The geological record of bison fossils that we recovered was “Bison dispersed into North America by a natural geographical consistent with the genetic record from the fossils,” says Froese. and ecological phenomenon—the Bering Land Bridge—about Froese and his colleagues have recovered bison and other 130,000 years ago when sea level was much lower than today,” remains from Yukon and Alaska sites for many years explained Froese. “They were so well adapted to the plains and had found several fossils in the Yukon that dated to a period ecosystem, they quickly colonized the continent.” of warm climate 125,000 years ago. “But because that was a time of high global sea level, they must have come over from Asia The bison invasion sometime prior to that when the Bering Land Bridge was Unlike other notorious invaders such as zebra mussels, purple exposed,” says Froese. loosestrife or Asian carp, bison were not introduced by humans. “We were fortunate with a fossil recovered from northern Yukon But their rapid spread and diversification are hallmarks of an that was found adjacent to a well-dated volcanic ash,” notes invasive species—and part of what make bison a keystone Reyes, who discovered the ancient fossil, Bison in the ecosystem. “In a way, North priscus, in northern Yukon. American bison are really an invasive species, though perhaps not in the common sense of the term,” said Froese. “They were International collaboration remarkably successful when they entered North America and interrupted a ecosystem that had been dominated by It took several years to yield the genetic story of these fossils. horses and mammoths for at least the previous million years.” Working with paleogeneticist Beth Shapiro at University of California Santa Cruz, the first efforts to recover DNA were not The paper, “Fossil and genomic evidence constrains the timing of successful. bison arrival in North America,” was published in Proceedings of the National Academy of Sciences in March 2017.

Source: Faculty of Science

URL: https://www.ualberta.ca/science/science-news/2017/march/researchers-trace-bison-to-common-ancestor-and-pinpoint-arrival-in-north-america